A method of this type is known from an article in "Supplement to the Grower" from Aug. 24, 1978 with the headline "Peter Bailey's drip system-cheap hydroponics", in which an amendment of the nutrient film technique (NFT) is described, which inter alia is used when cropping cucumbers.
The method described in the above article is based on a system known in Scandinavia using rock wool as growth substrate, and which is characterized by the use of bags in which the base is having a considerable slope. However, the method dealt with in the article does not employ steep slope of the base of the bags, and furthermore it avoids the use of rock wool. Instead a 2.5 cm layer of peat-moss litter is used or a capillary mat of a corresponding thickness, on which the plants in pots are placed for watering either from the top or from the bottom side by means of the capillary mat. The water is supplied through dripping either to the pots or to the mat, and as a consequence of the sloping base for the mat, the surplus water leaks out from the mat and runs through slits in the surrounding plastic sheet and further into a gulley.
Furthermore, an article in Financial Times on the 11th Jun. 1979 discloses a method, whereby growing bags located on a slightly sloping base is used for cropping for instance cucumbers and tomatoes. The bags may be filled with peat moss which is light and clean. This is equally true of pulverised bark which many regard as a more desirable medium since it is available in almost endless amounts, whereas peat moss is a natural soil which is available in a finite supply.
Recently, a dehydrated "board" of compost has been tested which only weighs about 3.5 kg and consequently is very easy to transport. It turned out that when wetted with about 18 l of water the board expands into a growing bag of an appropriate size in such a manner that when using a 1.2 m long bag it is possible to grow four tomato plants in a single growing bag.
An essential problem by using such growing bag is, however, that the growth substrate must posses an essential water retentiveness in order to maintain the growth substrate moistened thoroughly. Furthermore, such a water retentiveness retards the continuous exchange of water, whereby partly an insufficient supply of the nutrients and oxygen necessary for the growth of the plants to all the parts of the root system arises, partly a putrefaction may occur in the parts of the growth substrate wherein the supply of oxygen is insufficient.
DE-OS No.2,723,435 discloses a bag-shaped growing unit containing a granular plant growth substrate comprising plant soil or other growth substrates ready for use and which by addition of water with or without the addition of nutrients are made swelling.
These known growing bags are, however, encumbered with the serious drawback that they do not permit a continuous and automatically controlled supply of water and nutrients to the plant growth in connection with a recirculation of the watering water. The presence of soil and consequently of soil bacteria involves a serious risk of infection of all the plants in case they were watered by means of a common watering system. Moreover, the use of a hydrophilic growth substrate capable of swelling has turned out to imply root putrefaction as a consequence of an insufficient supply of air. Upon the swelling it is not possible to carry out the exchange of water, said exchange ensuring the necessary supply of both oxygen and nutrients. Furthermore, it turned out that the water is bonded so strongly to the hydrophilic growth substrates used in practice that in reality the major portion thereof is not available to the plant growth in such a manner that it may be absorbed by the plant roots.
Various other methods, devices and systems of this kind have been developed through the time, based on functions and constructions leaving the plant roots either immersed in the nutrient solution, such as e.g. disclosed in U.S. Pat. No. 3,739,522, or surrounded by a growth medium from time to time saturated with nutrient solution, e.g. by dipping said medium in the nutrient solution, such as disclosed in U.S. Pat. No. 4,118,891. In either situation, the exchange of nutrient solution around the roots is rather slow. As a result the supply of nutrients and oxygen to the roots as well as the removal of waste products from the roots is inadequate so that the conditions for the growth of the plant is unsatisfactory.
Experiments have shown that one of the decisive factors in the efforts of optimizing the growth of plants is that the conditions for the roots in taking up the water and exchange of the necessary amounts of nutrients and oxygen with waste products is as favourable as possible so as to minimize the stressing of the plants. Further, said experiments have shown that these conditions are favoured by a constant high percentage of relative humidity and oxygen accessible for the roots together with the maintenance of a steady but low concentration of the nutrients necessary in an accessible form and a lowest possible concentration of waste products including waste salts all around the roots. From said experiments it also appears that even very low concentrations of the nutrients could still be adequate as long as the concentrations are still maintained at a level sufficient to secure the desired uptake of the nutrients necessary.
Consequently, a continuous and fast exchange of the nutrient solution all around the roots is of the greatest importance in order to ensure a fast removal of waste products and a steady supply of fresh nutrients of the composition and concentration required at the same time as it provides for a high percentage of oxygen accessible to the roots. The main advantage resulting in carrying out a continuous and fast exchange of nutrient solution all around the roots is the possibility of minimizing the concentrations of nutrient salts and waste salts around the roots, thereby reducing the osmotic pressure outside the roots, which osmotic pressure is counteracting the uptake of water, at the same time as the necessary nutrient salts are still provided.
In U.S. Pat. No. 3,744,183 a method and an apparatus are disclosed in which the plants are suspended in the air by means of sponge-elements holding the root collars, and wherein the nutrient solution is fed intermittently or continuously by means of a vertically extending carrier member being in contact with the roots from two opposite sides thereof and being supplied with nutrient solution from the top of said carrier member. The apparatus is further provided with an outer supporting member and a system for collecting and recycling of the nutrient solution. In said method and apparatus, however, the apparatus used is quite open on top, and consequently a serious drawback is prevailing in that the water will evaporate at the top of the apparatus, especially from the sponge, the carrier member and the roots thereby leaving a nutrient solution with a higher concentration of salts around the roots and finally a depositing of cakes of salts around the top of the roots with the effect of serious damaging the roots and the growth of the plants. Furthermore, said apparatus is comprised by an outer supporting member as well as by an inner carrier member and a means for holding the plants therein, which is a rather complex and expensive apparatus.
The object of the present invention is to disclose an improved and simplified method for hydroponical growing of plants as well as an extremely simple apparatus and a system for practicing of said method.
The inventive method is characterized by comprising:
using an apparatus comprised by a pair of flatwise juxtaposed layers of watertight material, such as plastic film, defining at least one flat interspace for the development of the roots of a plant, said apparatus having a first closed end and an opposite second end and further being without any growth substrate therein, and said interspace being substantially closed to the surrounding atmosphere at least around the top of the root apart from minor openings for the plant stem and for the exchange of nutrient solution,
suspending said first closed end of the apparatus on at least one suspension means with the plane of the interspace vertically or slopingly oriented,
inserting plant roots inside said interspace at the upper part thereof, with the stem of the plant extending through a minor throughcut in one of said layers,
adding of nutrient solution to said interspace at a location above said roots of the plant and guiding it to said roots,
quickly percolating said nutrient solution down the roots, and
allowing unabsorbed nutrient solution to drain out from below the roots through at least one drain opening at a lower part of said interspace of the apparatus.
By this indicated method a quick exchange and percolation of the nutrient solution is obtained inside an almost completely closed interspace for the root, whereby the control of the root-environments is very easily carried out, and the depositing of salts at any place of the plant roots is avoided, and which is further well suited for the simultaneous growing of several plants under equal and constant conditions, as well as for growing of a single plant.
Preferably, the unabsorbed nutrient solution drained out from below the roots is recollected and recirculated in a per se known manner.
Preferably, this method is characterized by the use of a nutrient solution having a carefully controlled concentration of nutrients well below 2 per thousand, and by feeding nutrient solution in the amount of at least 0.1 l/h for each plant, preferably at least 0.25 l/h for each plant, whereby an extremely rapid growth of the plants is usually obtained.
Said method is also applicable in connection with an apparatus having a further suspension means for suspension of the apparatus with at least a part of the interspace or interspaces slopingly oriented, thereby broadening the range of apparatuses applicable and improving the adaptation of the apparatuses to the plants to be grown.
In using a very simple growing device comprising a flattened tubing suspended on a suspension means the upper part of said growing device is placed sloping proportional to the vertical plane containing the suspension means by means of a longitudinal displacement means. Thereby, in an initial phase of the growth, a good contact between the roots and the nutrient solution is ensured. In order to establish said sloping a displacement means, i.e. a wire, could be suspended below and sidewise displaced of the suspension means for the growing device, thereby supporting the upper part of the growing device in a sloping way.
The collection of percolated nutrient solution is simplified by using a flattened plastic tubing being closed alongside the bottom edge as well as alongside the top edge except for a discharge opening at the lowest point of the bottom edge.
In using a growing device having said pair of flatwise juxtaposed layers sealed together in intermediate lines or zones spaced in the longitudinal direction of the said layers and forming a series of transverse passageways between said zones for the passage of nutrient solution and development of the roots, a good contact between the roots and the nutrient solution is obtainable, even with a freely hanging growing device.
In a specially preferred embodiment of the method of the invention, an apparatus formed as a flattened plastic tubing is used as a growing device for a number of plants, said tubing being suspended along each of the two opposite closed longitudinal edges thereof on substantially parallel, horizontal extended suspension means, the intermediate part of the growing device sagging therebetween, thereby forming interspaces each sloping from a closed edge towards the middle of the device, plant roots being inserted into interspaces on either side of the middle and nutrient solution being added close to each suspended edge and percolated towards the middle of the tubing, and excess nutrient solution drained out through a drain opening at the lowest point of the center of the tubing, whereby a very favourable method of growing minor plants, such as lettuce, strawberries, beans, and a number of cut flowers, is obtained in which the plants could be placed all over the top surface of the growing device.
The inventive apparatus is comprising:
a pair of flatwise juxtaposed layers of watertight material, such as plastic film, defining at least one flat interspace for the development of the roots of a plant,
said interspace being substantially closed to the surrounding atmosphere, at least at the top of the roots, apart from minor openings for the insertion of the plant roots and the plant stem and for the addition and drainage of nutrient solution,
said apparatus having a first closed end and a second opposite end,
said apparatus further having means for guiding the added nutrient solution to the area of the inserted roots, said means for guiding not including a growth substrate,
and means for suspending the apparatus such that the nutrient solution added is allowed to quickly percolate the roots and drain out through the drain opening.
It is to be stressed that no growing substate at all is to be inserted between the two layers, and that, consequently, a very cheap apparatus is obtained, especially a growing device for simultaneous growing of a number of plants.
One preferred inventive apparatus intended for the growing of a single plant is
having the form of a flattened growing bag defining a single interspace being closed all around its circumference apart from a minor opening at its first end for the insertion of a plant and the addition of nutrient solution, and at least one drain opening at its opposite second end,
said growing bag having incorporated therein, as a means for guiding the nutrient solution, a thin coherent porous layer of water-distributing material selected from the group consisting of paper, glass wool, rock wool, foamed plastic, woven fiber-containing textile material, and non-woven fiber-containing textile material; and
said growing bag further having means for suspending the growing bag such that the nutrient solution added to the interspace of the growing bag through the opening at the first end passes over the said water-distributing material and the plant roots and drains out through the drain opening at the second end.
In this connection said thin coherent porous layer of water-distributing material is sized to fit the area of the interspace defined in said bag, thereby imparting a very secure passing on of the nutrient solution to the roots.
For many purposes, however, it has shown satisfactory when said thin coherent porous layer of water-distributing material is filling out only a minor part of the bag close to and alongside the first end of the bag around the opening for the plant stem and for the addition of nutrient solution, as the roots themselves gradually will take over the guiding of the nutrient solution inside the bag.
Advantageously, said suspension means includes an aperture in the two plastic layers at said first end of the growing bag, whereby said growing bag is very easily suspended by a string.
A preferred embodiment of the apparatus of the invention intended for growing of several plants is comprising:
a windable length of a pair of flatwise juxtaposed layers of watertight material, each of said two layers having first and second longitudinal edges,
the two layers being interconnected and sealed at least along said first longitudinal edges thereof and being adapted for suspension on a substantially horizontally extending suspension means alongside said first interconnected and sealed edges, thereby forming a growing device closed at top,
at least one of said two layers having minor throughcuts spaced along the length thereof and close to said first edge, for the insertion of plant roots,
said growing device being very easy to produce in endless form by extrusion.
A further preferred embodiment of the growing device of the invention is comprising:
a windable length of a flattened tubing of plastic film having opposed first and second closed longitudinal edges, said tubing being adapted for suspension on a suspension means alongside said first closed longitudinal edge thereof,
said tubing further being adapted for the insertion of a drip irrigation pipe inside said tubing alongside said first closed edge,
said plastic tubing further being adapted for the insertion of plantroots through minor spaced throughcuts through at least one of the two juxtaposed layers of said tubing, close to said first closed longitudinal edge, and
said plastic tubing being provided with a discharge opening for percolated nutrient solution at the lowest point of said second closed longitudinal edge,
said growing device especially being advantageous, as it is very inexpensive to manufacture, and which is especially advantageous for use in a slopingly suspended position in which a good contact between the roots and the nutrient solution is still ensured. Further, this embodiment is advantageous because of the further longitudinal passageway at the second closed edge for collecting and passing on of excess nutrient solution to the discharge opening.
A further advantageous embodiment of the inventive growing device is characterized in that said two layers of plastic are sealed in sealing-zones having a simple geometric form and spaced along the longitudinal direction of said layers and from the longitudinal edges thereof, said sealing zones thereby leaving longitudinally free passageways alongside said first and second edges and forming a series of successive transverse passageways open to said two longitudinally extending passageways, said transverse passageways having a substantially flat cross-section.
The resulting device is usable for simultaneously growing several plants and is advantageous in that a series of transverse passageways, each for the growth of one plant and for the percolation of nutrient solution therethrough is provided, thereby preventing some plants from predominating over neighbouring plants and minimizing the risk of spreading of disease between the roots.
The said growing device is intended for use without any growth substrate therein and in a vertically suspended position with the transverse passageways extending in a vertical plane. As a result a fast percolation of fresh nutrient solution through each transverse passageway is obtained, thus attaining optimum and uniform conditions for the growth of each plant.
The said device is of simple construction and inexpensively manufactured, as it is preferably made by simply welding together of a continuously blown plastic tube along the sealing zones followed by separating the tube into tubings of a length suitable for the purpose of the topic. Furthermore, the device is easy to instal and to use, thereby minimizing the total cost of growth of the plants. The said device may also be made of one or more lengths of plastic film put together in a flatwise juxtaposed position or of other bendable materials impervious to water, such as water-proof paper or other waterproof fibrous fabrics. The interconnections and sealings may be carried out in any known way. The material used is preferably of a type impenetrable to light. More preferably the material is of a light-reflecting type thereby minimizing the amount of heat collected in the growing device. In an advantageous embodiment of the growing device according to the invention the tubing may also comprise a heat-insulating material, such as a foamed or otherwise formed cellular film material, thereby reducing the heat transfer through the tubing and obtaining an economic use of heated nutrient solution.
A further preferred embodiment of the growing device of the invention is characterized by
a windable, flattened plastic tubing having two flatwise juxtaposed layers of plastic film, said layers being interconnected along opposing first and second closed longitudinal edges, respectively, of said flattened plastic tubing,
said two flatwise juxtaposed layers of the flattened tubing being sealed along two parallel longitudinal rows of sealing-zones located on either side of the center line of said flattened tubing, each sealing-zone in a row extending between a first point located some distance away from a closed edge of the flattened tubing, and a second point located further away from said closed edge and some distance away from the center line of the flattened tubing and on the same side thereof as said first point,
said rows of sealing-zones thereby leaving free longitudinal passageways each extending along the length of a respective one of said closed edges and a free longitudinal, central passageway extending between said two parallel rows of sealing-zones, said two rows of sealing-zones further forming two series of successive, transverse, flat passageways separated from each other by the sealing-zones, and each open to a corresponding longitudinal, outer passageway and to the longitudinal, central passageway.
This embodiment is particularly suitable for outdoor growing of plants, as it is very easily mounted in a stable position, so that the growing device can resist wind action. Depending on preselected arrangements, this embodiment moreover allows rainwater either to be collected and integrated in the growing system or to be discarded when needed. Depending on the culture grown, it is furthermore possible to grow an increased number of plants per unit length of the growing device without requiring a corresponding larger area of access to the plants by simply placing more plants along the length of each transverse passageway.
The sealing zones dividing up the growing device in transverse passageways have a simple geometric form, such as dots, rings or straight or curved lines extending perpendicular to, inclined to or parallel with the longitudinal direction of the length or tubing.
An embodiment of the growing device having two parallel rows of sealing zones, which is of particular interest from a manufacturing point of view is characterized in that the sealing zones of the two rows are formed as lines inclined to the longitudinal direction of the tubing in a substantially symmetrical way with respect to the center line. Thus the two sides of the growing device display the same properties during production as well as in use of the system.
In one embodiment of the inventive device having transverse sealing lines the transverse sealing lines are straight lines inclined at an acute angle of between 0.degree. and 90.degree., preferably between 0.degree. and 45.degree., most preferably about 10.degree., to the longitudinal direction of the device, thereby maintaining a relatively quick percolation of the nutrient solution through the transverse passageways, when the device is suspended with the transverse passageways oriented in a substantially vertical plane. In order to maximise the growing place left above the device within a predetermined level, e.g. inside the roof of a greenhouse, the angle should be as small as possible, whereby the height of the device between the upper and the lower, longitudinal edges thereof is as low as possible for a given length of the transverse passageways.
Depending on the type of plants grown, different proportions between the length and the width of the transverse passageways are recommended. For most purposes, however, it is satisfactory that the dimension of the transverse passageway from one longitudinal passageway to the other is about 3-5 times the dimension of the transverse passageway in the longitudinal direction of the device.
The choice of width of the longitudinal passageways between the closed edges of the tubing and the row of sealing zones depends on the manner of supplying the nutrient solution, for instance on the dimension of the supply pipes to be used, and on the space necessary for the roots and for the collection and outlet of the percolated water. For most purposes, however, it is satisfactory that the sealing zones extend between a distance of about 20-80 mm away from a first closed edge of the layers of the collapsed tubing. On the other hand, a considerably greater distance from the second edge or the center line of the layers or tubing may also be desirable, for instance 80-300 mm.
While the above simple form of the growing device functions quite satisfactory in most cases, it is occasionally advantageous to provide the growing device with additional longitudinal sealings along longitudinally extending sealing lines, each additional sealing extending from the end of a first sealing zone at the first point towards a neighbouring sealing zone to a point close to said neighbouring sealing zone and to the adjacent longitudinal passageway, said additional sealings thereby being gently inclined to the inside of the adjacent transverse passageways and leaving a passage from the adjacent longitudinal passageway to each of said transverse passageways for the inlet of nutrient solution therein.
This applies especially for devices having very wide transverse passageways separated by sealing zones extending perpendicular to the longitudinal direction of the device. The above arrangement ensures a correct delivery of the supplied nutrient solution to the area of the inserted roots. Any nutrient solution supplied by a supply pipe in the area of a transverse passageway between two adjacent sealing zones is transferred to said transverse passageway through the passage left by the additional, gently inclined, sealing line. Consequently, it is easier to place the plant in such a way that the supply of nutrient solution arrives at the area of the inserted roots.
It is worth underlining that the growing device is used completely without any kind of growing substrate inside the device, thereby eliminating all costs and other disadvantages therefrom. Moreover, storing and shipping costs are thus kept at a minimum. In addition all of the growing device as well as the plant material is burnable after use upon a short air-drying period.
According to a further feature of the invention the growing device is initially provided with a minor throughcut through at least one of the layers of the growing device at the end of each transverse passageway close to the longitudinal passageway at the first edge or to the longitudinal outer passageways, respectively, for insertion of a plant and, according to another feature, with at least one opening to the outside from the longitudinal passageway at the second closed edge of the device or the longitudinal central passageway, respectively, for the outlet of excess nutrient solution, thus expediting the correct mounting of the growing device. The throughcuts and openings can be provided prior to or during the mounting of the growing device.
A further object of the invention is to provide an improved system for hydroponical growing of plants, where a high degree of functional security is achieved, simultaneous with the cost of initial expenditure as well as the operating costs being kept at a very low level.
The inventive system is of the kind comprising
a collecting tank for a nutrient solution,
a control means for continuously measuring and adjusting the content of nutrient salts and other additives necessary for the growth of plants by adding the necessary amounts of water, macrosubstances, and microsubstances to the nutrient solution,
pumps and pipes for continuously carrying nutrient solution to the plants, and
at least one gutter for collecting and passing-on of used, excess nutrient solution from the plants to the collecting tank, said system further comprising
a number of apparatuses as claimed in claim 7,
a corresponding number of supply pipes, and
suspension means for suspension of the apparatuses,
said apparatuses being adapted for the insertion therein of a supply pipe or the outlets thereof in the interspace close to said suspension means.
The entire system is very simple in its construction. At the same time the mounting of the system and the insertion of the plants are performed in a very simple manner, thus saving a lot of time compared with other systems.
In an advantageous embodiment of the inventive system using a growing device as claimed in claim 13,
a supply pipe in the form of a drip irrigation pipe having spaced outlets is inserted in the longitudinal passageway of each growing device at the first closed longitudinal edge thereof,
said first edge of the growing device and said drip irrigation pipe being suspended on at least one suspension member, such as a cord or wire, stretched between at least two posts, the remaining part of the growing device depending therefrom,
the suspension means further including gripping means gripping around the suspension member and the upper part of the growing device holding the drip irrigation pipe at suitable places along the length thereof, thereby fastening the growing device to the suspension member,
said suspension member being positioned at a level sufficient for keeping the bottom of the growing device just above the top of the gutter.
As a result a very simplified and reliable system is obtained, in which the growing device is kept at a correct position by the suspension member without subjecting the supply pipe to stresses. Moreover, the growing device with supply pipe is easily mounted at or removed from the suspension member.
In a further advantageous embodiment of the said system
the suspension means comprises two parallel wires, tightly stretched between two posts and kept close to each other on either side of the growing device beneath the supply pipe inserted therein, and
the suspension means further comprises gripping means, such as hooks, inserted under the wires and the supply pipe and suspended by strings fastened to a mounting means above the growing device,
thereby supporting the growing device and the plants inserted therein,
the top of said plant being fastened to the string.
The use of this construction enables the positioning of the growing device between the two wires with the first longitudinal passageway including the supply pipe situated just above the wires. This results in a very stable suspension of the growing device. The growing device could of course also be suspended on a single wire positioned inside the upper longitudinal passageway alongside the supply pipe therein.
Despite the suspension wire or wires being tightly stretched, the wires are slightly bowed in a downward direction when loaded with the growing device. Consequently, the lower, second longitudinal passageway is sloping downwards from both ends of the growing device towards the middle thereof, the latter being at the lowermost position. Naturally it is advantageous to place this point above the gutter and to provide the outlet from the second longitudinal passageway at this point.
When using the inventive system for growing plants subjected to wind, said system is advantageously characterized by a further supporting means supporting each growing device against being forcibly removed from the substantially vertically suspended hanging position. In this connection one embodiment of said further supporting means comprises at least one suspension member stretched between abovementioned posts at a level above the lower longitudinal passageway, and a number of locking elements, such as hooks, clamps, straps or pins, securing the growing device to the supporting means.
Further in connection therewith anchoring means holding the growing device, such as strings, nets or tapes, may be fastened at anchoring blocks or suspension members secured below the growing device.
In a system comprising growing devices having two rows of sealing zones the suspension means advantageously comprises at least one suspension member or weighting member pressing or weighing down the central part of the growing device so that it can resist wind action. Said weighting member may advantageously be at least one sandhose placed loosely on the central part of said growing device, or it may be comprised by a supply pipe placed outside of the growing device and having small irrigation pipes extending therefrom, each irrigation pipe having an outlet placed inside the interspace of the growing device, above the roots of an individual plant therein.
In a particularly advantageous embodiment a system including a growing device with two rows of sealing zones comprises an outer plastic tubing surrounding said growing device and carried by an intermediate carrying means, said outer plastic tubing being closed at each end of the growing device thereby substantially forming a miniature greenhouse around said growing device.